Simple bone cysts, also known as unicameral bone cysts, are fluid-filled cavities within bone that typically occur in the long bones of children ages 4-10. They enlarge during growth but become inactive after skeletal maturity. Active cysts develop near the growth plate and can cause pathologic fractures. Treatment involves curettage to remove the cyst lining and bone grafting to prevent fractures and reduce the risk of recurrence.

1. Simple Bone Cyst (Unicameral)
Maryam Sharifian
MSc student of O&P at Isfahan University Of
Medical science
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2. Discussion
a membrane lined cavity containing a clear yellow fluid.
 occurrs most often in children 4-10 years of age;
 lesions remain asymptomatic unless complicated by
fracture.
 they enlarge during skeletal growth and become inactive,
or latent, after skeletal maturity.

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3. Active cysts
Develop in patients under 10 years of age
• Cyst arises adjacent to growth plate & may grow to
fill most of metaphysis
Bone may be slightly expanded within
cortical shell
• May cause pathologic fracture
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4. Passive cysts
patients are usually over 12 years of age
cysts cease to expand
become increasingly separated from growth plate (more
than 1-2 cm)
have thicker bony wall than active lesions
may show evidence of healing or ossification
less likely to result in fx
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5. Causes…
 The cause of a unicameral bone cyst remains unknown.
Theories have been proposed but none have been definitively
proven.
 One of these theories is that the cysts result from a disorder
of the growth plate.
 Another is that the cysts result from problems with
circulation that are caused by a developmental anomaly in the
veins of the affected bone.
 The role trauma plays in the development of these cysts is
unknown.
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6. Symptoms…
 Unless there has been a fracture, bone cysts are without
symptoms.
 They may occasionally be discovered by chance on x-rays
obtained for other reasons.
 There is no mass or tenderness unless there is a fracture.
 There may be an abnormal angulation of the limb secondary
to the fracture or shortening of the limb if the adjacent
growth plate is involved.
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7. Location
lesion appears to arise from the growth plate & in early stages, lesion is lies
adjacent to growth plate;
• typically the simple bone cyst will have a central location, whereas an
ABC will have a slightly eccentric location;
- predilection for the metaphysis of long bones;
- proximal humerus (50% of cases)
- proximal tibia
- proximal femur (40%)
- foot:Calcaneal Bone Cysts
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8. Radiographs
show a central, well marginated & symmetric radiolucent defect
in metaphysis
metaphyseal bone does not remodel normally
metaphysis is broader than normally seen but not broader than
with width of epiphyseal plate
thin rim of non reative bone borders the unicameral bone cyst
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9. Radiography
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11. Differential Diagnosis
Fibrous
dysplasia
Aneurysmal
bone cyst
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• Monostotic fibrous dysplasia is usually
eccentric rather than central and diaphyseal
rather than metaphyseal
• Periosteal reaction is greater in fibrous
dysplasia than simple bone cyst;
• Enlarge metaphysis to greater than width
of the epiphyseal plate;

12. Histologic Examination
Active cyst have a mesothelial
membrane lining thin margin of bone
Inner wall of bone adjacent to
membrane may be lined by osteoclasts
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Between membrane & osteoclasts is a layer
of areolar tissue containing fibroblastic and
multinucleated giant cells

13. Treatment
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• Simple cysts are treated with curettage
and bone grafting
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• Goal of treatment is prevention of
pathologic fracture
• Recurrence is high for active cysts (50%)
& low for latent cysts (10%)

14. Thank you
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